Suggestion for a HAMMER feature

Matthew Dillon dillon at
Mon Sep 21 08:41:36 PDT 2009

:Hi guys,
:Being forced to use Solaris and ZFS, I found a few, what seem to be easy 
:things to add to Hammer:
:1) Make df -h list show how much space is used by each PFS
:2) Make df -h show how much space is taken up by historical data and how much 
:is taken up the the "current" data and combined.
:3) in hammer info show how much historical data is being stored.
:4) Maybe an equvalent of "zfs list" ?
:Would these be simple to add in?

    They are all good ideas but not entirely trivial to add.  Basically
    we would need to track it in the PFS data structure but also be able
    to update it in-place (like we do with ATIME) without rolling a
    new B-Tree element, and the changes have to be synchronized using the
    undo FIFO.  So the PFS data structure would have to be expanded
    a bit and logic added to deal with it.

    Otherwise though the actual tracking is fairly straightforward.  Any
    B-Tree element with a delete_tid is counted towards historical data
    and any B-Tree element without a delete_tid is counted towards current
    data, for whatever PFS that record resides in.

					Matthew Dillon 
					<dillon at>

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